Multiple-way connection for transmission lines



March 25, 1930. p. MITCHELL ET AL ,7 1,

MULTIPLE WAY CONNECTION FOR TRANSMISSION LINES Filed Aug. 23, 1928INVENTORS i lmclwzzmza Silent ATTORNEY Patented Mar. 25, 1930 UNITEDSTATES PATENT OFFICE DOREN MITCHELL, OF NEW YORK, AND HAROLD C. SILENT,OF LARCHMONT, NEW

YORK, ASSIGNOIRS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A COR-PORATION OF NEW YORK MULTIPLE-WAY CONNECTION FOR TRANSMISSION LINESApplication filed August 23, 1928. Serial No. 301,659.

This invention relates to transmission lines and more particularly to animproved method of and means for establishing a multi-way connectionbetween a plurality of such lines.

By a multi-way connection is meant an arrangement whereby two-waycommunication may be established between a subscriber connected to oneline and a subscriber connected to any of the other lines. In thearrange ments of the invention repeater apparatus 1n-- cluding the usualrepeater elements, balancing networks and hybrid coils, is utilized forestablishing a multi-way connection. Two of the transmission lines areinterconnected ba a two element'two-way repeater. Across t e networkterminals of the hybrid coils of this repeater will be bridged a circuitinclud ing the windings of a hybrid coil. The third transmission linewill be connected to this latter hybrid coil.

The arrangements of the invention have the advantage that a multi-wayconnection may be established between a plurality of lines, whichconnection utilizes only two repeater elements, while at the same timeaffording desired amplification features between all of the lines. Otherfeatures of the invention consist in the provision of means foradjusting impedance values to give desired transmission quality. Furtherobjects and features of the invention will appear more fully from thedetailed description thereof hereinafter given.

The invention may be more fully understood from the followingdescription together with the accompanying drawing, in the Figures 1 and2 of which are shown one form of the invention and a modificationthereof. Similar reference characters have been utilized to denote likeparts in both figures of the drawing.

In Fig. 1 are shown two transmission lines A and B interconnected by awell known type of repeater a paratus, which com risesv hybrid coil 5 isa third transmission line C.

It is pointed out that with the arrangements.

passing on to line C. Similarly, transmis sion from C to A will beampified by the opposite gain element R of the repeater in passing fromC to A. In like manner, transmission from B to C would be over a pathcomprising hybrid coil 2, repeater R hybrid coil 1, bridged circuit 3,and through hybrid coil 5 to line 0. Transmission from C to B would takeplace over a path comprising hybrid coil 5, bridged circuit 3, repeaterR hybrid coil 2, and line B.

Included in the bridged circuits 3 and 4 are the pads 6 and 7 These areloss producing networks. These pads or networks may have such a value ofloss as to make the loss from A to C bear the desired relationship tothe loss from A to B, i. e., the loss between any two subscribersconnected to the circuit may be made always the same, or varied as de-'approximately the line impedance and that the impedance connected to therepeater terminals should match approximately the impedance of therepeater. To this end the correcting networks 8 and 9 may be connectedbetween the line and the repeater and the net work N and repeater,respectively. To prevent unbalancing the repeater similar correctingnetworks may be connected between the repeater and circuit 3 and betweenthe repeater and network N or suitable alterations may be made in thepad 6 and the network N Similar impedance correcting networks 10 and 11are shown associated with line B'and the auxiliary balancing networkNC".

An alternative arrangement for establishing a multi-way connection inaccordance with the principles of theinvention, is shown in Fig. 2.Similar reference characters have been utilized to denote like partswith respect to Fig. 1. The two lines A and B are interconnected by atwo element repeater, as heretofore. giis repeater comprises the gainelements a 1 and R the balancing networks A N and N and the hydrid coils1 and 2.

The bridged circuits 3 and 4 are also provided. However, instead ofbeing bridged across the network side of the hybrid coils 1 and 2, thesecircuits are associated therewith by the hybrid coils 14 and 15,respectively. The lines A and B and the auxiliary balancing networks Nand N are also connected to the hybridcoils 1 and 2 by means of thehybrid coils 12 and 13, respectively. With such an arrangement, it ispointed out,

.the division of energy ismade through the agency ofhybrid coils in sucha manner that the impedance termination of the bridged circuit to theline is not materially impaired. Hence, the impedance correcting pads 8,9,

10 and 11 may be eliminated. In other rements for transmission inopposite directions,

circuits connected to the network side of each of said hybrid coils andterminating in the windings of another hybrid coil, and a third linesection connected to said last mentioned 7 hybrid coil.

2. Two line sections interconnected by re.- peaten apparatus comprisinghybrid coils,

alancmg networks, and repeater gain elementsfor transmission in oppositedirections, circuits connected to the network sideof each of said hybridcoils andterminating in the windings of a third'hybrid coil, lossproduc- 1ng devices in each of said circuits, and a eater apparatuscomprising hybrid coils, alancing networks, and repeater gain elementsfor transmission in opposite directions, circuits connected to thenetwork side of each of said hybrid coils and terminating in thewindings of a third hybrid coil, auxiliary balancing networksconnectedto the line side of each of said first mentioned hybrid coils forbalancing said last mentioned circuits, impedance correcting devicesassociated with said lines and auxiliary balancing networks forcorrecting the impedance relations between said lines and saidrepeater'apparatus, and a third line vsection connected to said thirdhybrid coil. 1

In testimony whereof, we have signed our names to this specificationthis 22nd day of August 1928.

DOREN MITCHELL. HAROLD C. SILENT third line section connected to saidthird hybrid coil.

3. Two line sections interconnected'by repeater apparatus comprisinghybrid coils, balancing networks, and repeater gain ele-' ments fortransmission in opposite directions,

circuits connected to the network sideof each of said hybrid coils andterminating in the windings of a third hybrid coil, auxiliary balancingnetworks connected to the line side of each of said first mentionedhybrid coils for balancing said last mentioned circuits, and a thirdline section connected to said third hybrid coil.

4. Two line sections interconnected by re-'

